From a93b768eeafcc155b62d58e0b62264cf39eb386a Mon Sep 17 00:00:00 2001
From: Anna Kozlova <anna.kozlova@jetbrains.com>
Date: Thu, 23 Aug 2018 20:53:55 +0300
Subject: [PATCH] unused class when used through import only should not be
 treated as used (IDEA-99444)

---
 .../daemon/impl/analysis/RefCountHolder.java  | 21 ++++++++++++++++---
 ...rClassImportShouldNotLeadToClassUsage.java |  8 +++++++
 .../daemon/LightAdvHighlightingJdk6Test.java  |  4 ++++
 3 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting6/InnerClassImportShouldNotLeadToClassUsage.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/RefCountHolder.java b/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/RefCountHolder.java
index 7fd16c8e05b9..c061b8e6f162 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/RefCountHolder.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/RefCountHolder.java
@@ -43,7 +43,10 @@ import org.jetbrains.annotations.Nullable;
 
 import java.lang.ref.Reference;
 import java.lang.ref.SoftReference;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicReference;
 
 class RefCountHolder {
@@ -172,8 +175,20 @@ class RefCountHolder {
   }
 
   private void registerLocalRef(@NotNull PsiReference ref, PsiElement refElement) {
-    if (refElement instanceof PsiMethod && PsiTreeUtil.isAncestor(refElement, ref.getElement(), true)) return; // filter self-recursive calls
-    if (refElement instanceof PsiClass && PsiTreeUtil.isAncestor(refElement, ref.getElement(), true)) return; // filter inner use of itself
+    PsiElement element = ref.getElement();
+    if (refElement instanceof PsiMethod && PsiTreeUtil.isAncestor(refElement, element, true)) return; // filter self-recursive calls
+    if (refElement instanceof PsiClass) {
+      if (PsiTreeUtil.isAncestor(refElement, element, true)) {
+        return; // filter inner use of itself
+      }
+      PsiImportStatementBase importStmt = PsiTreeUtil.getParentOfType(element, PsiImportStatementBase.class);
+      if (importStmt != null) {
+        PsiElement resolve = importStmt.resolve();
+        if (resolve != null && PsiTreeUtil.isAncestor(refElement, resolve, false)) {
+          return;//filter refs on inner members in imports
+        }
+      }
+    }
     synchronized (myLocalRefsMap) {
       myLocalRefsMap.putValue(refElement, ref);
     }
diff --git a/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting6/InnerClassImportShouldNotLeadToClassUsage.java b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting6/InnerClassImportShouldNotLeadToClassUsage.java
new file mode 100644
index 000000000000..86b9ed647e1d
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting6/InnerClassImportShouldNotLeadToClassUsage.java
@@ -0,0 +1,8 @@
+package p;
+
+import static p.Outer.Inner;
+import java.util.*;
+
+abstract class <warning descr="Class 'Outer' is never used">Outer</warning> implements List<Inner> {
+  public static class Inner {} 
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/LightAdvHighlightingJdk6Test.java b/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/LightAdvHighlightingJdk6Test.java
index 0e8d79415d19..2329b0b7af0b 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/LightAdvHighlightingJdk6Test.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/LightAdvHighlightingJdk6Test.java
@@ -107,4 +107,8 @@ public class LightAdvHighlightingJdk6Test extends LightDaemonAnalyzerTestCase {
   public void testPrivateClassReferencedInAnnotationOnSibling() {
     doTest(false, false);
   }
+  
+  public void testInnerClassImportShouldNotLeadToClassUsage() {
+    enableInspectionTool(new UnusedDeclarationInspection(true));
+    doTest(true, false); }
 }